GOF mutations in JAKs (JAK1, JAK2, JAK3) and STATs (particularly STAT3 and STAT5B), as well as alterations in cytokine receptors (IL7R, CRLF2) and negative regulators (SOCS1, PTPN2), are recurrent in myeloproliferative neoplasms and certain lymphoid cancers. The gene discussed is JAK2; the disease is lymphoma.